As others say, US made M193 (Win/Fed/LC/etc) tends to all be about the bottom of the barrel of quality. You have to go to Russian steel to get worse. In decreasing order of importance it comes down to:
-how evenly and uniformly is the lead distributed in the jacket, (voids or anything else that will cause the 1/4 Million RPM spinning bullet to be out of balance, will wreck accuracy more than anything.
-how consistent is the lead total mass in that jacket,
-how consistent is the shape of the bullet,
-how consistent in the powder charge pushing the whole thing
-How consistent is the brass dimension and metallurgy and tension also can matter, for most US ammo, they already blew it before we get to that part.
US made M193/M855 does the bare minimum to meet spec on those bullet quality specs, and as a result, have shitty accuracy. Wolf Gold tries to half-ass a little less than the US plants, and so has better ammo. Just look at the back of the bullets for starters. Good 55 FMJ like Hornady bullets, will have a nice consistent and uniform lead portion surround by the copper jacket; and correspondingly tend to shoot pretty darned good. Cheap crap USGI spec bullets will have unevenly distributed smeared lead of varying visible depths from bullet to bullet.